Light sensitive paper and method of treating same



Patented Apr. 1938 LIGHT SENSITIVE PAPER AND METHOD OF .TREATING SAME Clyde A. Crowley, Chicago, and George H. Goodyear, Evanston, 111., assignors to The Huey Company, Chicago, 111., a corporation of Illi-.

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No Drawing. Application April 30, 1937, Serial No. 139,950

type described in our U. S. Patent No. 2,093,421 and hereinafter described, is not used, the color is not sufliciently deep.

However, when a paper coated with the above type of sensitizer is treated with this special type of predeveloper, an exceptionally fine print will result. For example, the so-coatedsheet should be developed in a solution suchas the following 4 Claims.

Our invention relates to light-sensitive paper and to a predeveloper therefor, and particularly relates to a novel'coating for blue print paper and to a chemical compound adapted for use in 5 the treatment thereof.

A developer of the type intended for use in the described relation is disclosed in our Patent No. 2,093,421, September 21, 1937.

One of the principal problems in the manufactureof blue print paper is that of providing a coating therefor having a known stability or permanency under adverse climatic conditions;

in other words a paper that the manufacturer may .distribute with the assurance that it will remain effective for. at least a known period,

preferably over one year. The desire, and in many cases the necessity for a certain degree of permanency has been responsible for the general use of a coating compound that is relatively go slow in action and which does not produce bright 'or intense blue color without bleeding and the resultant partial obliteration of the white lines.

An object of our invention is, therefore, to provide a perfectly stable coating, one that operates to completely eliminate bleeding in development and one in which an intense blue is present in the final product, and a paper which prints at greater speed than products heretofore known.

The improvement is brought about by the use so of a novel coating containing some of the usual components, but in which a substance that acts as a catalyzer to accomplish the needed results, is incorporated. The catalytic agent which we have discovered is ammonium nitrate.

35 Although the above catalyst may be added to the known types of blue print sensitizing solutions with beneficial results, in practice we prefer to formulate sensitizing solutions particularly adapted to take advantage of the catalytic reaction induced by this substance.

One sensitizing solution that has been found to be appropriate and satisfactory is as follows, the formula providing for a bath of approximately five (5) gallons.

1. Potassium carbonate oz 11 2. Oxalic acid oz 11 3. Ammonium nitrate oz 8 4. Ferric ammonium oxalate.- lbs.. 8

5. Potassium ferricyanide oz 6 5o 6. Water, to bring the solution to 145 B.

A paper sensitized with the above solution will not produce good prints when developed in the ordinary manner, due to its low potassium ferri- 55 cyanide content. If a special predeveloper of the and then be washed and treated with an oxidizing solution and rinsed.

. Potassium carbonate oz Oxalic acid oz Disodium phosphate Glucose oz Potassium ferrocyanide"--. lbs Sodium bisulphite oz Water, to make gals A number of other satisfactory predeveloper solutions are disclosed in our said Patent No. 2,093,421. Another satisfactory solution is as follows:

1. Potassium carbonate oz 2. Oxalica oz 3. Disodium phosphate (NazI-IPO4J2H2O) oz 4. Sucrose I 024.. 5. Potassium ferrocyanide lbs 6. Sodium bisulphite oz 7. Water, to make gals When the exposed paper is washed in a solution such as above defined, the excess of ferrous iron in the exposed portions reacts with the ferrocyanide ofthe predeveloping' solution to form ferro-ferrocyanide.

The concentration of the ferrocyanide/ion in the developer is great enough so that no ferrous iron has the opportunity to In practice, sodium bisulphite has beenfound satisfactory.

A further improvement in the brilliance of the print is achieved by decreasing the particle size of the pigment on the paper.

This is done by means of aliphatic polyhydroxyl compounds, aliphatic aldehydes and aliphatic ketones incorporated in the predeveloper which will not react with iron salts to form insoluble reaction products. In practice, various sugars are-satisfact ry.

In order to obtain good whites with the ferrocyanide predeveloper, it is necessary to bufier the acid concentration rather carefully. Any of the common acid buffers are satisfactory, pro-, vided they do not have too powerful oxidizing or reducing properties; Inuse are mixtures of potassium oxalate, potassium acid oxalate and 1. Ammonium nitrate g 3 2. Citric acid g 6 3. Ammonium oxalate g 6 4. Ferric ammonium oxalate g.. 42 5. Potassium ferricyanide g 7.5 6. Water, to make cc 250 This formula is for development in the customary manner involving washing and treatment with an oxidizing agent.

In all cases the inclusion of the catalyst improves the s'peed and the blue color, improves the ease of washing the paper and stabilizes the sensitizing solution against deterioration during storage, as well as stabilizing the paper thus coated against rapid spoiling under normal or adverse atmospheric conditions.

The possible actions of the catalyst above disclosed in effecting the results described have been the subject of extensive laboratory study aimed at determining the'probable mechanism by which these substances produce the desirable efiects described. Observations as made, in our opinion, restrict the action of the substance claimed to the field of catalysis.

We claim:

1. The method of making blue prints which consists in coating a paper with a solution comprising a light-reduceable ferric complex, a ferricyanide saltand ammonium nitrate as a catalyzer that will stabilize said coating, then exposing parts of said paper to light and then treating said paper in a predeveloper comprising an acid reacting water solution of a ferrocyanide.

2. The method of making blue prints which consists in coating a paper with asolution comprising a light reduceable ferric complex, a ferricyanide salt and ammonium nitrate, then exposing parts of said paper to lightand then developing said paper. 3. The method of making blue prints which consists in coating a paper with a solution comprising alight-reduceable ferric complex, a ferricyanide salt and ammonium nitrate, then exposing parts of said paper to light and then treating said paper in a predeveloper comprising an acid reacting water solution of a ferrocyanide.

4. A coating for blue print paper comprising a light-reduceable ferric complex, a ferricyanide salt and ammonium nitrate.

CLYDE A. CROWLEY.

GEORGE H. GOODYEAR. 

